Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus62 ktbw 240054 
afdtbw

Area forecast discussion
National Weather Service Tampa Bay Ruskin Florida
854 PM EDT sun Apr 23 2017

Update (overnight and monday)...
00z water vapor and h4 rap analysis shows southern stream
shortwave energy that crossed the southern half of the
Florida Peninsula today beginning to exit into the Atlantic,
with deep layer subsidence and drying overspread the
Florida Peninsula in its wake. Further upstream, a large
closed upper low feature can be seen spinning over the Tennessee
Valley this evening. Associated with this system, a surface
cold front trails southward into the northeast Gulf of
Mexico. Regional radars show that this front is supporting
areas of showers and storms across the the Carolinas/Georgia
and into the Florida Panhandle. However, further south from
here, the shower activity becomes very limited over the NE
Gulf as the convection becomes removed from the best
synoptic lift/qvector convergence ahead of the upper low,
and the updrafts encounter fairly hostile thermodynamic
conditions above 10,000 feet.

This situation looks to hold through the overnight into
Monday morning as the whole system shifts eastward and the
front approaches the Florida West Coast. A few scattered showers
can not be ruled out, and the forecast will show 20-30% rain
chances through Monday morning, however, the hostile
conditions aloft and the continued main synoptic influence
staying along and north of the I-10 corridor suggests that
measurable rainfall for all is highly unlikely, and those
that do see a showers will certainly not consider the
amounts a drought-buster.

Those down toward The Fort Myers area were lucky enough to
see some good rainfall earlier Sunday associated with the
passing shortwave trough mentioned above, but not much
more additional rain should be expected with this next
system.

The last of the widely scattered showers will exit the
region toward midday as the cold front moves into the
Atlantic. Much of Monday will be characterized by more
clouds than sun and a developing gusty northwest wind. The most
clouds should be closer to the coast as conditions appear to
favor quite a bit of statocu migrating onshore. The further
inland one GOES, and the further into the diurnal heating
cycle we get, these stratocu should transition to a sct-bkn
cumulus field. Little chance of any diurnal showers Monday
afternoon...as the synoptic flow will far overpower/prevent
any defined sea-breeze, and the moisture layer will become
ever more squeezed/shallow from above.

Those with boating plans on Monday, either on the eastern
Gulf, or an Inland Lake, should be prepared for rather gusty
northwest winds, sustained in the vicinity of 15 knots with gusts
likely over 20 knots at times. So, rather choppy conditions
developing Monday on the water as we head through the
morning hours and through the entire afternoon.

&&

Aviation (24/00z through 25/00z)...
potential for any isolated sea-breeze showers seems to be
diminishing. Will have prevailing VFR through the remaining
evening hours. Good potential for developing/lowering cigs
late overnight, and have included all terminals with MVFR
cigs between 09-14z. Some potential klal/kpgd might see a
period of IFR, however, confidence too low to include in
this taf package. Cold front slides through region Monday
morning with winds increasing and becoming gusty during the
mid/later morning hours. Gusts over 20kts are likely through
a good portion of the day out of the west and northwest behind this
front. Post-frontal setup would suggest quite a bit of
statocu off the Gulf through the day. Therefore, continued
periods of MVFR 2-3kft bases will be possible after 14z
through at least the early afternoon.

&&

Marine...
a cold front crosses the eastern Gulf of Mexico late
tonight into Monday morning. A few scattered showers accompany the
frontal passage...but no widespread rainfall or thunderstorms
expected. Winds increase by later Monday morning and remain at
0r near cautionary levels through Monday evening. High pressure
builds in Tuesday...providing lighter westerly winds.

&&

Prev discussion... /issued 258 PM EDT sun Apr 23 2017/

Short term (rest of today-monday)...
an upper low near the south-central Mississippi Valley this
afternoon tracks southeast to the Georgia/SC border. A short
wave trough over southern Florida lifts northeastward and is
absorbed into troughing from the upper low. At the surface a
low in northern Georgia trails a cold front south across the Florida
Panhandle then southwestward over the Gulf of Mexico. The
surface low move to the Carolina coastal waters by late Mon
afternoon with the front sweeping into the East Gulf tonight
then across the state Mon. In response to the front and the
upper level short wave trough...a surface trough over The
Straits from western Cuba to the northern Bahamas lifts
northeast and merges in the Carolina surface low.

The deepest moisture...model precipitable water values at 2 inches or more...
which resulted in some record rainfall in the south has shifted
away. However enough residual moisture...precipitable water in the 1.5 to 2 inch
range...and instability remain which along with sea breeze
convergence and limited day time heating to support a chance of
showers and a slight chance of thunderstorms through the rest of the
afternoon. There should be a break in rainfall from late afternoon
or early evening through the later night hours. But expect some
cloudiness along with patchy late night fog...especially in areas
that received rain. Slightly deeper moisture returns with the front
but limited with precipitable water in the 1 to 1.5 inch range...enough for
scattered showers or a few thunderstorms. The front and associated
weather begin to impact...the Nature Coast in the pre-dawn
hours...the Tampa Bay area around sunrise...southwest Florida around
mid-afternoon...then exits by late afternoon. Winds will pick
noticeable with the front but will mainly be of concern for
aviation/marine interests.

Middle term/long term (monday night-sunday)...
Monday night into Wednesday the mid/upper level shortwave trough
will continue to move up along the eastern Seaboard away from the
region followed by ridging gradually build over Florida as a
deepening trough sets up over the western half of the Continental U.S. Late in
the week through the weekend. At the surface weak high pressure will
be over the area for Monday night through Thursday, then late in the
week into the weekend a stronger high pressure will build in from
well out in the Atlantic Ocean. For Monday night into Tuesday night
a low level west to northwest flow will be in place bringing some
cooler and drier air into the region under fair skies. During
Wednesday and Thursday the flow will shift to south to southwest
with limited moisture continuing across the region so expecting
mostly clear to partly cloudy skies with rain chances less than 10
percent. For Friday through Sunday the low level flow will shift to
southeasterly with moisture gradually increasing leading to some
additional clouds. There will be a slim chance, less than 20 percent,
for a light shower/sprinkle Friday, then over the weekend some more
moisture could move into the region leading to a few showers, but
will keep rain chances at around 20 percent at this time as moisture
does not look that deep. Temperatures will be close to normal for
Monday night and Tuesday then as the ridging builds aloft we'll see
a gradually warm up a couple of degrees each day reaching the mid
80s coast to the lower 90s inland for Friday through Sunday.

Fire weather...
recent heavy rainfall...especially in the south...along with more
limited rain as a cold front moves through late tonight and during
Mon will provide enough moisture to preclude any low relative humidity concerns for
the next few days.

$$

&&

Preliminary point temps/pops...
tpa 70 77 65 80 / 10 20 0 0
fmy 69 80 65 82 / 10 20 0 0
gif 67 79 60 83 / 20 20 0 0
srq 70 76 64 80 / 10 20 0 0
bkv 66 76 56 81 / 20 20 0 0
spg 70 76 65 79 / 10 20 0 0

&&

Tbw watches/warnings/advisories...
Florida...none.
Gulf waters...none.

&&

National Weather Service Glossary of Abbreviations